In lakes and rivers leaf litter input from the coastal vegetation represents a major nutrient load and plays a basic structural and functional role in several ecosystems. Leaf litter decomposition is usually studied under natural circumstances or in the laboratory, but not in class "A" evaporation pans. This new, pioneer method was chosen to investigate decomposition rate and evaporation together. An experiment was carried out to study leaf litter decomposition in class „A” evaporation pans. Litterbags were filled with leaves of two species (Salix and Populus) and placed into the water. The aim of the study was to determine the decomposition rates of leaves and daily evaporation. Decay curves were well characterized by the exponential decay model. There was no significant difference between the decomposition rates of leaf litter bags and plankton net bags. Exponential decay coefficients of the leaves were in the fast and medium category. Evaporation of the control pan correlated to air temperature better, than leaf litter pans. Ep of leaf litter pans was higher, than control pans. The average values of the water chemical variables corresponded to similar values in the Carpathian Basin. The publication is supported by the EFOP-3.6.3-VEKOP-16-2017-00008 project. The project is co- financed by the European Union and the European Social Fund. We acknowledge the financial support of Széchenyi 2020 under the EFOP-3.6.1-16-2016-00015.